1. Field of the Disclosure
The present disclosure relates to an accelerator-pedal reaction force control apparatus which controls a reaction force of an accelerator pedal of a vehicle, that is, a force necessary to depress the pedal (i.e., reaction force against the depression of the accelerator pedal).
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2005-132225 describes a technique for increasing a pedal reaction force of an accelerator pedal in a transition period in which an operational state with a low specific fuel consumption (high fuel efficiency) is changed to an operational state with a high specific fuel consumption (low fuel efficiency). An example of such a transition period is a period in which the state of a lock-up clutch is changed (switched) from an engaged state to a disengaged state in a vehicle including an automatic transmission. Thus, information regarding the change in the operational state to an operational state with low fuel efficiency can be presented to the driver, so that the driver can be suppressed from performing an accelerator operation which causes the change in the operational state to an operational state with low fuel efficiency. As a result, the fuel efficiency may be increased.
However, if the pedal reaction force is increased in the transition period in which the operational state is changed to the operational state with low fuel efficiency, such as the operational state in which the lock-up clutch is disengaged, the following may occur. That is, when, for example, the driver passes a vehicle in front while driving at a high speed, the accelerator opening degree is frequently increased and reduced in a relatively short period of time. In such a case, the accelerator pedal may be operated such that it is largely depressed, is returned, and is then depressed again. When the accelerator pedal is depressed the first time, the pedal reaction force is increased in the transition period in which the operational state is changed to the operational state with low fuel efficiency. Then, the increase in the pedal reaction force is eliminated when the accelerator pedal is returned. Then, the accelerator pedal is depressed again to increase the accelerator opening degree. At this time, if the driver is still under the influence of sensation of the temporal increase in the pedal reaction force in the previous transition period, the driver feels as if the accelerator pedal is lighter than usual. Therefore, the driver tends to depress the accelerator pedal by a larger amount than usual and unnecessarily increase the accelerator opening degree. In other words, it was found that there is a possibility that the increase in the pedal reaction force in the transition period for increasing the fuel efficiency will induce an excessive increase in the accelerator opening degree in the subsequent period. The excessive increase in the accelerator opening degree leads to sudden increase in a vehicle speed and an engine rotational speed, which cause reduction in the driving performance, exhaust performance, and fuel efficiency performance.